DNA and Genetic Engineering

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DNA and Genetic Engineering
DNA replication refers to the process through which a DNA doubles during cell division. This starts by unzipping the double helix of the molecule facilitated by the helicase enzyme which helps in breaking the hydrogen bonds. Next, a replication fork is created through the separation of single strands. The leading strand is oriented towards the 3’ to 5’ replication fork direction. The lagging strand is oriented away from the fork in 5’ to 3’ direction. On the leading strand, a primer which is produced by the primase enzyme attaches itself on end. This forms the first point for the synthesis of DNA. Through a continuous replication, the DNA polymerase gets attached to the “leading strand” and moves along it as it adds complementary nucleotide bases in the 5’ to 3’ direction. On the lagging strand, the primase enzyme makes many RNA primers and binds them at different points along the strand. Following the 5’ to 3’ direction, Okazaki fragments are attached to the strand in a discontinuous form of replication. When the bases get matched up, A to T and C to G, the exonuclease enzyme removes the primers, and the gaps are filled by complementary nucleotides. Proofreading of the strand is then carried out to ensure it is perfect. The DNA ligase enzyme combines the sequence into continuous double strands. This leads to two DNA molecules with each DNA having half part as new and the other half as old. The new DNA then ends up as a double helix.

In eukaryotes, the origin of DNA replication is difficult to identify. This is because depending on the system, any or specific DNA sequence can cause replication.
There are many possible mutations in a genome. One example is a substitution. In substitution, there is an exchange of one base with another. This is similar to changing a chemical letter for example by switching G to A. A substitution may cause a codon change that may lead to producing of a changed protein. An example of this is sickle cell anemia which results from substitution in a gene referred to as bet-hemoglobin. Another example of gene mutation is Frameshift. This happens when a loss or addition of DNA bases results in a change in the reading frame of a gene. The change may be caused by an insertion or deletion making the message distorted hence unclear. An example is an alteration on the sentence “The fat cat sat.” to “hef atc ats at.” Some cancers, Tay-Sachs disease, cystic fibrosis, and Crohn’s disease have been associated with this form of mutation.
Genetic engineering is the procedure of modifying the DNA of an organism’s genome. It may involve deleting a DNA region, changing a base pair or introducing a gene copy. Genetic engineering is carried out through gene-editing technology which involves the efficient and precise modification of DNA within a cell. An example of gene editing technology currently under study is human cloning. This involves two different applications which are reproductive cloning and research cloning. Research cloning is also referred to as “somatic cell nuclear transfer (SCNT).” The SCNT process involves the transfer of a nucleus to a female egg that has had genetic material removed. A clonal embryo is produced at the end of the process. In reproductive cloning, a clonal embryo is made but rather than being used in research; it is implanted womb for growth. Cloning is also involved in embryonic stem cell research.
Works Cited
“What Is DNA Replication?” Yourgenome.org, The Public Engagement Team at the Wellcome Genome Campus, 25 Jan. 2016, www.yourgenome.org/facts/what-is-dna-replication.
“What Is Genome Editing?” Yourgenome.org, The Public Engagement Team at the Wellcome Genome Campus, 23 Aug. 2017, www.yourgenome.org/facts/what-is-genome-editing.
Ardekani, Ali M. “Genetic Technologies and Ethics.” Journal of medical ethics and history of medicine 2 (2009).
Gilbert, David M. “Making sense of eukaryotic DNA replication origins.” Science 294.5540 (2001): 96-100.
Understanding Evolution team. “Types of Mutations.” Understanding Evolution , evolution.berkeley.edu/evolibrary/article/mutations_03.